I want to get absorption spectra of a molecule using VASP. I know how to perform GW calculations for solids using VASP? But no clue how to do it for molecules? I do not find any example online.
In general, VASP is written for solid-state calculations. However, you can put the molecule in the center of a large box (the dimension of box should be (roughly) at least 10 times bigger than the interatomic distances). In this way you can manipulate VASP to consider your molecule as a periodic solid and do the calculation.